That may have something to do with falling gas prices. I think that the lousy economy is another factor in it as well.
That stupid idiot Transportation Secretary and those loons in congress should raise the frigging gas tax while gas is low... or turn the whole enchilada to the states. They act is if this revenue "shortfall" is going to be a permanent fixture while collections are only down in proportion with miles driven.
If they say otherwise, I bet they're cooking the books like the shysters, hucksters and criminals they are.
Motorists should be sick and tired of departments like NHTSA raiding the transportation trust fund. The NHTSA has absolutely nothing to do with transportation and almost everything to do with the energy problems that we are facing. Because of their stupid regulations, cars are 500 lbs heavier than they were 10 years ago and 1000 lbs more than they were 20 years ago.